P25 Unknown Opcodes

[mtindor]

I use DSDPlus for monitoring P25 systems. I think pretty much nobody knows what these unknown opcodes are (or haven't released that info publicly). Good chance that SDRTrunk, OP25, DSD-FME do not know what they are either. But I'm throwing the question out here anyway.

This is from the latest DSDPlus logfiles. Just wondering if anyone has a clue what these opcodes are. If they were known, that may be beneficial to all authors of P25 trunktracking software. Pretty sure SDRTrunk also does not know what these opcodes are. Don't know about DSD-FME or OP25.

CC Monitoring - Ohio MARCS P25 (Motorola)
2023.11.17 10:18:57 Sync:+P25p1 NAC:341 TSDU Opcode= 5 MFID=90 05 90 40 80 C0 00 00 00 08 00
2023.11.17 10:18:57 Opcode= 9 MFID=90 09 90 0D C0 00 00 00 00 00 00

CC Monitoring - AEP P25 (L3 Harris)
2023.11.17 9:05:52 Sync:+P25p1 NAC:01A TSDU Opcode= 1 MFID=A4 81 A4 11 0D 83 4E 84 2A 84 EE
2023.11.17 9:05:52 Sync:+P25p1 NAC:01A TSDU Opcode=15 MFID=A4 8F A4 0A 25 00 0A 00 00 00 00


Voice Call monitoring Voice channel - Ohio MARCS P25 (Motorola)
2023.11.17 10:14:13 Sync:+P25p1 NAC:341 TDULC UNHANDLED EXPLICIT OPCODE: #5 9000000000000000

Voice Call monitoring Voice channel - AEP P25 (L3Harris)
2023.11.17 9:25:07 Sync:+P25p1 NAC:01A TDULC UNHANDLED EXPLICIT OPCODE: #10 A400FFFFFC95899

 

[maus92]

Can you verify that the OP codes were decoded properly? How often are they repeated?

 

[mtindor]

Can you verify that the OP codes were decoded properly? How often are they repeated?

They were decoded the same/regularly every time. Were they decoded "properly"? I can only assume. Pretty sure SDRTrunk also doesn't know what those same opcodes are. So at least two pieces of software do not. I'll verify that about SDRTrunk when I can.

The CC unknown opcodes show up every time the full system information is announced over the CC (whether its Motorola P25 or L3Harris P25), and as you know that happens constantly, repeated at regular intervals.

The VC unknown opcodes occur every time there is a voice call for the Ohio MARCS P25 (Motorola) that I monitor. The unknown opcode for AEP P25 (L3Harris) occurs any time there is a voice call and any time there is a certain type of data call occuring.

I'll try to gather some info from SDRTrunk to correlate / verify when I can. What I provided above is all from DSDPlus.

Mike

 

[maus92]

If you see them regularly, at least you know the the data probably isn't getting mangled during transmission. I have decode issues from time to time due to my physical location, wx conditions and the pulsing nature of the L3/Harris P25 system I primarily monitor. UT2 regularly adds garbage system channels - and garbage systems probably due to malformed data packets.

 

[mtindor]

DSDPlus and SDRTrunk log lines where CRC failed. I always omit them when looking at this stuff. In SDRTRunk, lines that passed as decoded properly have "PASSED" on the log line. Those that fail have "FAILED" on the log line.

I haven't posted anything from SDRTrunk yet though.

Mike

 

[GTR8000]

Might want to give Unitrunker 2.1 a shot, I suspect that you'll find some of these messages are being decoded. Expand your horizons, young man. 😉

 

[mtindor]

Might want to give Unitrunker 2.1 a shot, I suspect that you'll find some of these messages are being decoded. Expand your horizons, young man. 😉

LOL. I can't fathom adding another one to the mix. I'm too confused already. Maybe though. Been so long since I have used UT. Does it provide adequate logging of the good and bad, known and unknown?

Mike

 

[GTR8000]

I mean, if you're going to ask what some of the "unknown" opcodes are, you should probably first look at one of the oldest trunking decoding programs out there, no? 🤔

 

[mtindor]

I mean, if you're going to ask what some of the "unknown" opcodes are, you should probably first look at one of the oldest trunking decoding programs out there, no? 🤔

Well, maybe so. But I have never used it on a P25 system and don't know how long it has supported P25 P1 / P2 or how much attention has been given to the elusive vendor specific opcodes and things like that which aren't published publicly. Good point though. I'm looking on the group. Is the download link on unitrunker.com for 2.1 "download latest" actually the latest, or will I need to get the latest from within the group?

 

[GTR8000]

2.1.0.105 is the latest. Modify the URL if necessary.

 

[dave3825]

Been so long since I have used UT. Does it provide adequate logging of the good and bad, known and unknown?

You could say adequate.

 

[GTR8000]

I would say that Unitrunker 2.1's logging of control channel and traffic channel (FDMA only) data is quite good, actually. The full opcodes are preserved and Rick has provided very detailed descriptions of each control channel opcode when known. More than adequate.

 

[GTR8000]

By the way, regarding two of the control channel opcodes @mtindor posted, I identified those years ago. They are the 05 90 and 09 90, both of which are MSI ASTRO 25 specific (note that the 90 indicates the MFID for MSI).

05 90 is Motorola System Broadcast that broadcasts certain system parameters to the subscribers
09 90 is a Motorola Scan Marker broadcast

As for the 15 90 opcode on the traffic channel for the ASTRO 25 system, that should be the OTA alias being encoded, and there should've been multiple (4) in a row broadcast for that particular opcode. Each message represents a portion of the alias string.

 

[KE6UVW]

I just got interested in getting into the nitty gritty of digital radio, but as far as p25 goes you might want to go through one of the P25 protocol training manuals online. I'm using one from Codan Radio Communication. Of course knowing the p25 protocol wont necessarily tell you the specifics of any particular agency's implementation but it'll give you some hits as to what it might be.

 

[boatbod]

I use DSDPlus for monitoring P25 systems. I think pretty much nobody knows what these unknown opcodes are (or haven't released that info publicly). Good chance that SDRTrunk, OP25, DSD-FME do not know what they are either. But I'm throwing the question out here anyway.

This is from the latest DSDPlus logfiles. Just wondering if anyone has a clue what these opcodes are. If they were known, that may be beneficial to all authors of P25 trunktracking software. Pretty sure SDRTrunk also does not know what these opcodes are. Don't know about DSD-FME or OP25.

These are manufacturer-specific opcodes (i.e. mfid != 0) thus not part of the official P25 spec. That aside, there are many P25 opcodes that op25 (and I assume other softwares) choose not to decode simply because they are of little or no relevance to voice monitoring. Some manufacturer-specific opcodes are of interest (e.g. tg patches) and where known these are going to be decoded and acted upon.